Hi Mr. Grogg,
It's not detrimental per se. All of the mechanics you've described are fine. I've personally run ACKS with everything from straight 3d6 to the crazy Unearthed Arcana system of 9d6, 8d6, etc. Chargen is very much a matter of taste.
I will say that I think point-buy is not a good idea for games that aim to have any sense of simulation. Random ability scores result in a world wherein not every character conforms to stereotype, in a way that point buy systems never do.
Let me give an example of what I mean. Assume you are creating a fighter, and you get to assign 18, 16, 14, 13, 10, 10 as your attributes. Here is what 90% of players will create:
S 18, C 16, D 14, I 10, W 13 Ch 10; or S 18, C 14, D 16, I 10, W 13, Ch 10; or S 14, C 16, D 18, I 10, W 13, Ch 10 (for the archer lovers). They might move the 13 to Ch or Int. But that's basically how the stats are going to be allocated.
This trend became painfully obvious in 3.5, when players calculated the mathematically best placement of ability scores using the normal array, elite array, and each level of point buy. Optimizers would routinely chide players for sub-optimal allocation. Etc.
With purely random ability scores, though, you might get a character who looks like this:
S 16, C 14, D 13, I 10, W 10, Ch 18; or
S 13, C 18, D 10, I 16, W 13, Ch 10; or
S 18, C 10, D 10, I 13, W 10, C 16; and so on
It makes the game world richer and more realistic if sometimes you have a fighter who's clumsy but charismatic; or not as strong, but very cunning; or iron-willed and charismatic, but with a weak constitution; and so on. Such persons populate our history books, yet - in the absence of random rolls - they will never populate our game worlds.
I agree with you that our PCs/adventurers should represent the better-than-average human being. ACKS' recommended system is to roll 3d6 in order, generating 5 characters, and then pick the best 1. That gives you a character who is in the top 20% of the human race, but it emerges organically, rather than by fiddling with the dice.
If you want to be more heroic, roll up 10 character, and pick the best 1. For "chosen one" campaigns, roll up 100 characters and pick the best 1. (With an automated character generator, it's pretty easy to do that sort of thing).